My Tire Experience
Just wanted to share some tire observations. Soon after I bought my Saturn I lost a tire due to a nail hole near the side wall, and then shortly after another due to a tear. One tire is a match for what was on the car- Firestone FR380, the other is an off brand(cheap) marketed through Firestone shops- Primewell PS830.
Both tires had 10/32" tread depth new. The Firestone tire, with a 55K warranty and 400 treadwear rating, has 6/32" left after 42879 miles. The Primewell tire, with a 40K warranty but a 460 treadwear rating, has 7/32" left after 41719 miles. Both tires share an axle on the rotation schedule. Miles were equally divided between rural chip seal coated (pea gravel) town roads, a worn concrete county highway, city driving, and divided highways with wide range of pavement qualities.
Pressure was maintained at 40 psi on the Primewell (36 psi sidewall max), and 45 psi on the Firestone (44 psi sidewall max) for the first 30K miles, then up to 50 psi all around for the remainder. The exception was for heavier snowfalls, where I dropped to 35 psi for a total of no more than 1k miles.
Most should know that treadwear ratings are not concrete predictors, but good for comparison. Note that the 55k warranty tire is wearing faster than the 40k, giving some credence to each tire's treadwear rating. The cheaper Primewell is nosier, perhaps after extending rotation on the rear axle too long, though I cannot see or measure uneven wear. The Firestone was more forgiving of my neglect, still running as quietly as a lesser brand can be expected.
My conclusion- I continue to be convinced that Heat Kills Tires. Everything else is secondary.
Through this experience, and my experience with large truck tires, inflation has proven the key to mpg AND tire life. To me, heat wear/damage caused by underinflation is nearly as costly as fuel consumed due to underinflation. Can an overinflated tire be more susceptible to impact damage? Yes, but the inflation pressure and load (weight) on the tire have to exceed the design specs of the tire to show a significant correlation. How often are cars overloaded? On the flip side, I think one could argue that underinflation heat can compromise the integrity of a tire, making it susceptible to impact damage.
So thanks to everyone who pounds the max psi drum.